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Metal hose joint structure and brazing characteristics - focus on microfluidic control technology

Metal hoses are widely used in thermal power plants for the transportation of dry fuel oils, insulating oils and turbine oils. The medium delivered by the hose has a higher pressure and temperature. Therefore, if the welding site leaks or is desoldered, it will cause a serious accident. The metal hose has two inner and outer layers, and the inner layer is a small φφφ20 x2mm hose. The outer layer is a woven fine steel mesh, and the two layers are made of 1Cr18Ni9Ti. The hose mainly serves as a sealing function, and the thin steel mesh serves as a strength protection. There are currently three types of hoses manufactured by the manufacturer (spiral monolithic, seam welded and brazed). Since the metal conveying hose on the power station boiler is subjected to high temperatures and pressures during operation, it is often subjected to bending stress. Therefore, it is recommended to use a spiral integral hose. After the hose is transported to the site, a stainless steel short pipe joint is added to the hose, and a stainless steel outer ring is added to the thin steel wire for brazing. The brazing joint must ensure the sealing and pressure of the pipe during operation. The brazed structure has the following characteristics: The shape of the brazing wall is relatively complicated, and there are corrugated, fine steel mesh, etc. As shown in Fig. 1. In order to ensure the sealing and bearing capacity of the brazed joint, the quality of the brazing is high, and it has sufficient stability in mass production. Since the corrugated hose and the thin steel mesh are thin and thin, manual brazing with oxyacetylene flame is very likely to cause overheating. If it exceeds 830 °C, it will form a stable chromium and an oxide which is difficult to remove, making brazing almost impossible. Therefore, it is required to prevent oxidation during the brazing process. In the practice of welding production, it is often difficult to meet the design and process requirements due to the special hook and non-reporting factors. To properly solve this problem, we have adopted a new arc brazing process. That is, when performing the arc arc brazing under the protection of an inert gas, the arc is located between the workpiece and the melting electrode, and the surrounding is a shielding gas. The solder acts as an electrode for the arc.

The brazing zone is continuously fed from the welding torch to form a filler metal for the brazing weld. Melting pole arc brazing is characterized by low melting point of solder (2% ring silver solder melting point of 8600 ~ 900 ° C), high mechanical strength, small heat affected zone of welding. Brazing does not need to use a corrosive effect. No need to clean after welding. Easy to operate. Easy to automate

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